Why Southeast Greenland's glaciers have slown down since 2005

I'm in San Francisco for the annual meeting of the American Geophysical Union, the world's largest gathering of climate scientists. I saw ten or so great talks yesterday (and five really boring ones!) Here's a summary of the the most interesting talk I heard yesterday:

If you plan on owning ocean front property after the year 2050, you should pay close attention to the glaciers In Greenland. Greenland holds enough ice to raise global sea level by over 20 feet (6.5 meters), should its ice cap completely disintegrate--though such an event would likely take centuries to occur. Still, should the climate warm 2°C or more this century, partial melting of the Greenland Ice Sheet could readily raise global sea level by a meter or more by 2100. That's why scientists reacted with concern during 2003 - 2005, when all of the glaciers in southeastern Greenland accelerated in synchrony to speeds 30% to 210% faster than they had flowed in 1996. As they sped up, the glaciers began dumping huge amounts of ice into the ocean off the coast of southeast Greenland, more than doubling Greenland's contribution to global sea rise, to .57 mm/year. Would the glaciers keep accelerating, bringing about an increasing disintegration of the Greenland Ice Sheet? Nobody knew, since computer models of glacial dynamics were (and still are) in a primitive state.

Figure 1. Helheim Glacier in southeast Greenland, in three images captured in 2004, 2005, and 2006. The glacier accelerated significantly in 2005, and the face of the glacier retreated 5 km inland (middle frame) compared to 2004. However, by the summer of 2006, the acceleration ceased, the the glacier returned back to its 2004 position. Image credit: Ian Howat, University of Washington.

Well, it turned out that 2005 was the peak of the glacial acceleration event. The glaciers in southeast Greenland have returned to where they were eight or nine years ago--still causing a net loss of mass that is raising global sea level, but not as fast as in 2003 - 2005. In a talk titled, "Ocean regulation of glacier dynamics in south-east Greenland and implication for ice sheet mass changes",Tavi Murray and colleagues from the UK's Swansea University presented a plausible theory for why this strange synchronous speed-up and slow-down occurred. Using satellite, aircraft, and surface observations, the researchers found that air temperatures in the region did not vary much over 2003 - 2005 (Figure 2). Thus, a major increase in temperature could be ruled out as the cause of the glacier surge. However, study of the ocean temperatures near the coast revealed strong clues that ocean currents were responsible for the surge.Figure 2. Ocean currents off the east coast of Greenland feature the cold East Greenland Coastal Current flowing north to south (white arrows) and the warm Irminger Current flowing south to north (red arrows). Image credit: Arctic Climate Impact Assessment.

Ordinarily, the southeast coast of Greenland features a cold water current flowing north to south, called the East Greenland Coastal Current (EGCC). Much of the cold water for this current is supplied by melting of the 14 glaciers in southeast Greenland that empty into the sea (two of these glaciers, Kangerdlugssuaq and Helheim, represent 35% of east Greenland's total glacial discharge). A few hundred kilometers offshore, a warm water current called the Irminger Current flows the opposite direction, bringing warm water from the North Atlantic northward. In 2003, it happened that weather conditions over Greenland brought an unusually low amount of run-off of precipitation. With little new mass pushing the glaciers seaward, the glaciers responded by greatly reducing the amount of ice they dumped into the ocean by the shore. As a result, the East Greenland Coastal Current slowed down and warmed, which allowed the warm Irminger Current to advance towards the coast, warming the coastal waters even more. All that warm water near the coast began melting the glaciers where they reached the sea, causing the glaciers all along the southeast coast of Greenland to accelerate and rapidly thin between 2003 - 2005. By 2006, the thinning glaciers had dumped so much new ice into the ocean near the coast that the waters cooled and the East Greenland Coastal Current re-established itself. This cooled the glaciers at their marine termination points and slowed down the glacial surge, putting the glaciers back where they had been before 2003. This is a classic example of a negative feedback process--a change in weather conditions which generates a response, but the response creates conditions that tend to dampen the response.

Figure 3. Average temperatures for the only station in southeast Greenland with a century-long temperature record, Angmagssalik (called Ammassalik on the map in Figure 2). Temperatures in southeast Greenland during the 1930s and 1940s were similar to today's temperatures, suggesting that glacial surges like we witnessed in 2005 may have also occurred in the 1930s and 1940s, before we had monitoring capability. Image credit: NASA Goddard.

CommentaryAs I commented in my previous post, Arctic sea ice loss appears to have created a new atmospheric circulation pattern that brings more warm air in the Arctic, creating a positive feedback loop that causes even more sea ice loss. This positive feedback loop was a bad news surprise that our climate models did not predict. Now we have evidence of a good news surprise that no model predicted--a negative feedback loop that acts to keep the southeast portion of Greenland's Ice Sheet from runaway glacial acceleration. We can expect many more surprises--good and bad--over the coming decades, as our climate responds to the huge shove human activities are giving it.

Ricky Rood in CopenhagenOur Climate Change expert, Dr. Ricky Rood, is in Copenhagen for the COP15 climate change treaty negotiations. His latest post, called Have you no sense of decency, sir, at long last? makes for very interesting reading on how the U.S. is "wasting its intellect and time on disruptions designed to play to people at home".

Next postI'll have another post from the AGU meeting Thursday or Friday this week.

About 20 years ago this ol wore out carpenter was having drinks with an elitist old newspaper publisher friend of mine. He looked at me with suprise when I was able to discuss Atlas Shrugged at length.I told him, "Don't judge a man by the calluses on his hands, it's the calluses between your ears you need to watch out for".

Quoting AwakeInMaryland:156. OH, I don't know any of them. I wasn't even born yet; I was just a gleam in my daddy's eye. (now imagine that with wink, BIG HAIR, and southern accent, learned from friends and neighbors, KY southward.)

P'colaDan -- have you been following conversation per P'colaDoug, myself, regarding your TAP WATER? Eek. If you don't have a simple filter, please get one. See the front page of your Pensacola paper today!

Just took a short break to check in, so if I don't respond...I did finally get out to lay in those snow supplies! (It's like carrying an umbrella around here...maybe...prob. not...then get slammmed...ice, yeek!)

Yes I have and thought it was interesting how quickly the article appeared in the paper. When I was growing up we had very soft water here, tasted great and took forever to get soap off you during a shower. Left here in '78 and returned in '88 and there was a HUGE difference. Water tasted awful (still does) and soap is gone almost before you put it on. And on a related subject, read an article little bit ago that says people had to leave a hotel because of Legionnaires disease. Seems the hotel water filtration system was too good. Got rid of all the chlorine and this allowed bacteria to build up.

statements in absolutes about Climate Change are ridiculous and should be considered for what they are: exercises in mental onanism (look it up).

Sorry about how long I took to get back on this posty, but I'm back at the office after three weeks off and I'm trying to catch up

About 20 years ago this ol wore out carpenter was having drinks with an elitist old newspaper publisher friend of mine. He looked at me with suprise when I was able to discuss Atlas Shrugged at length.I told him, "Don't judge a man by the calluses on his hands, it's the calluses between your ears you need to watch out for".

156. OH, I don't know any of them. I wasn't even born yet; I was just a gleam in my daddy's eye. (now imagine that with wink, BIG HAIR, and southern accent, learned from friends and neighbors, KY southward.)

P'colaDan -- have you been following conversation per P'colaDoug, myself, regarding your TAP WATER? Eek. If you don't have a simple filter, please get one. See the front page of your Pensacola paper today!

Just took a short break to check in, so if I don't respond...I did finally get out to lay in those snow supplies! (It's like carrying an umbrella around here...maybe...prob. not...then get slammmed...ice, yeek!)

Quoting tornadodude:♪ Oh, the weather outside is frightful ... but the Colts and Saints are so delightful ... All the others already know … 13 and 0, 13 and 0, 13 and 0… Oh, they don't show signs of stopping ... and the fans are really hopping ... getting ready for the really big show .... Superbowl … Superbowl ... Superbowl! ♪♪♪

Quoting tornadodude:♪ Oh, the weather outside is frightful ... but the Colts and Saints are so delightful ... All the others already know … 13 and 0, 13 and 0, 13 and 0… Oh, they don't show signs of stopping ... and the fans are really hopping ... getting ready for the really big show .... Superbowl … Superbowl ... Superbowl! ♪♪♪

♪ Oh, the weather outside is frightful ... but the Colts and Saints are so delightful ... All the others already know … 13 and 0, 13 and 0, 13 and 0… Oh, they don't show signs of stopping ... and the fans are really hopping ... getting ready for the really big show .... Superbowl … Superbowl ... Superbowl! ♪♪♪